ABSTRACT
The literature regarding chemotherapy for patients with unknown primary cancers is relatively scant and requires interpretation in light of the many limitations of the available data. These patients represent an extremely heterogeneous population with respect to age, clinical presentation, sites of metastasis, functional status, and histology. Difficulties in classification has limited cooperative group studies and only in the last several years have a few investigators performed prospective therapeutic trials in groups of these patients. Treatment has improved for many specific subsets of these patients as our knowledge has continued to evolve, with an increasing ability to separate groups with important therapeutic implications. The details of the various clinical and pathological subsets of patients, which have now been fairly well characterized, have been summarized elsewhere (1,2). The classification and further deliniation of various groups also continues to evolve and is likely to expand considerably with the use of molecular techniques such as gene expression profiling. Unfortunately, most patients with well-differentiated
or moderately differentiated adenocarcinoma and poorly differentiated carcinomas of unknown primary site do not correspond or fit into one of the several favorable prognostic clinical or pathological subgroups.
